Technical Field
This invention relates generally to thermal compensation, and more particularly to thermal compensation in image projectors.
Background
Improved contrast can be achieved in a projection system by modulating the illumination light incident on the spatial light modulators (SLMs) of the projection system. For example, if a pixel of an SLM is to display 5% brightness and is illuminated at full brightness (100%), then the pixel must attenuate 95% of the illumination light. Light leakage inherent in most SLMs makes it difficult to achieve dark levels when significant attenuation is required. On the other hand, if the pixel is illuminated at 10% brightness, then the pixel need only attenuate 50% of the incident light to achieve a 5% brightness level, and light leakage by the pixel is much less significant.
In order for the pixel to achieve accurate display levels, the intensity of the light incident on the pixel must be known with a high degree of precision. If the intensity of the incident light varies from the expected intensity, the output of the pixel will also vary, thereby degrading the quality of the projected image.